Which window frame material leads to superior environmental performance?

SANTA BARBARA, CA - High-quality window systems help insulate a building, reduce overall energy use, and improve its environmental footprint. But how do different window frame materials compare in thermal insulation performance, and how often do they need replacement? Which window frame materials exhibit superior environmental performance over their entire life cycle?

In a study commissioned by Cascadia Windows & Doors Ltd., VitalMetrics found that fiberglass window frames conserve 68% more heating and cooling energy than typical vinyl (PVC) window frames, and conserve 87% more energy than thermally-broken aluminum frames. While the difference in annual emissions between fiberglass and PVC frames is less than 3 kg of CO2e per square foot of frame, the greenhouse gas emissions associated with energy loss are much greater for an aluminum frame, approximately 234% greater than PVC and 471% greater than fiberglass.

On average, aluminum window frames have a service life of about 40 years while PVC frames last about 22 years. Fiberglass window frames boast a service life of more than 80 years, meaning two aluminum frames and four PVC frames are needed to do the same job as one fiberglass window frame. Not only does this increase replacement frequency, but total primary energy needs also increase due to the manufacturing of new frames and disposal of frames at the end of their service life.

For context, if all 37,100 high schools in the United States had 400 windows that were switched from PVC window frames to fiberglass frames and then used for 80 years, the mitigated energy loss would be equivalent to taking 14 million passenger cars off the road for one year. These findings indicate that adopting fiberglass window frames on a large scale may have a substantial impact on overall building efficiency. Read the full case study here.

  Life cycle primary energy consumption of one window frame,  including embodied energy, use phase energy loss, and end-of-life management energy requirements. Sudden increases in energy consumption indicate window frame replacement and represent the energy required to dispose of the old frame as well as manufacture a new one. Source: IERS, LLC 2018.

Life cycle primary energy consumption of one window frame, including embodied energy, use phase energy loss, and end-of-life management energy requirements. Sudden increases in energy consumption indicate window frame replacement and represent the energy required to dispose of the old frame as well as manufacture a new one. Source: IERS, LLC 2018.